A wide variety of products, especially food products like meat, sausages, cheese and the like, are often offered in visually attractive packages made of two webs (namely, a lower web and an upper web) using a vacuum skin packaging process, a thermoforming process or other methods.
The lower web is typically used as a support for the product and may be flat or heated and thermoformed to the desired shape, thus forming a receptacle for the product to be packaged. The lower web typically comprises a rigid or semi-rigid substrate, such as for instance of a plastic or cardboard material, and a sealing layer. The upper web is typically a flexible and formable film with a sealing layer that, in the end package, faces the sealing layer of the lower web.
Various forming machines are known in the art.
U.S. Pat. No. 6,896,506 discloses a thermoforming machine including a loading station configured to load a thermoplastic billet onto a frame. The frame has an outer ring and a billet support blade defining a channel therebetween. The billet support blade engages the billet to maintain the billet on the frame during heating of the billet. A heating apparatus is configured to heat the billet and a forming station is configured to form the billet into a container. In one embodiment, a preheating station may be utilized to perform initial heating of the billets. Such initial heating may be desired when a coining press is utilized to create an initial structure on the billet, such as adding a rim around the peripheral edge of billet.
U.S. Pat. No. 4,836,764 discloses an apparatus for the thermal pressure forming of plastic blanks into containers which includes several elements. A heater brings the plastic blanks to a melt phase by heating them to a melting temperature sufficient to relieve internal stresses therein. A conveying arrangement takes the plastic blanks through the heater. Thereafter, a press forms the plastic blanks into retortable containers.
U.S. Pat. No. 4,563,325 discloses an apparatus and method for producing articles by stretch-forming or pressure-forming of thermoplastics in the solid crystalline phase which permits forming from a billet of given thickness articles of greater wall thickness than would be formed by stretch-forming or pressure-forming the clamped billets.
U.S. Pat. No. 3,947,204 discloses an apparatus for making thermoplastic containers. The apparatus takes a measured amount of thermoplastic material which is lubricated, heated and forged into a desired shape preform with a predetermined lip configuration. The center portion of each said preform is maintained at a forming temperature while the peripheral portion thereof is clamped and rapidly brought below the softening point of the plastic resin. Blanks are forged in a forging means having a cooled lip forming means.
U.S. Pat. No. 3,546,746 discloses an apparatus for forming flanged hollow articles of work-strengthenable plastic materials. The outer edge of a blank is gripped around its periphery against a transverse seat.
U.S. Pat. No. 3,502,310 discloses a hot plate billet heater and method of heating.
U.S. Pat. No. 7,481,640 discloses a scrapless thermoforming machine including a plurality of transport trays having frames configured to hold thermoplastic billets and billet clamps.
U.S. Pat. No. 5,035,600 discloses an apparatus for converting thermoplastic blanks into shaped articles having a wheel-shaped conveyor which carries an outwardly extending link for a coupling which can engage successive blanks of a series of blanks during advancement along a first portion of its endless path.
U.S. Pat. No. 4,352,766 discloses a scrap-free, substantially solid phase, relatively low temperature process for rapidly making plastic articles from resinous powders wherein the resultant articles can comprise various polymers
NL 8501418 relates to a blow or vacuum moulding acrylic plastic roof dome.